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An AA battery also called "double A" or Mignon battery is a standard size of a single cell cylindrical dry battery; in the IEC system it is designated size "R6". AA batteries are commonly used in portable electronic devices. An AA battery is composed of a single electrochemical cell that may be either a primary battery (disposable) or a rechargeable battery. The exact terminal voltage and capacity of an AA size battery depends on the cell chemistry. AA batteries account for over 50% of general battery sales.
The AA battery size was standardized by the American National Standards Institute (ANSI) in 1947, but had been used in flashlights and electrical novelties for some time before formal standardization. Battery nomenclature gives different designations, depending on cell size and chemistry. For example, a zinc–carbon (Leclanché) AA cell is designated "15" by ANSI and R6 in the IEC system.
An AA cell measures 49.2–50.5 mm (1.94–1.99 in) in length, including the button terminal—and 13.5–14.5 mm (0.53–0.57 in) in diameter. The positive terminal button should be a minimum 1 mm high and a maximum 5.5 mm in diameter, the flat negative terminal should be a minimum diameter of 7 mm.
Primary (non-rechargeable) zinc–carbon (dry cell) AA batteries have around 400–900 milliamp-hours capacity, with measured capacity highly dependent on test conditions, duty cycle, and cut-off voltage. Zinc–carbon batteries are usually marketed as "general purpose" batteries. Zinc-chloride batteries store around 1000 to 1500 mAh are often sold as "heavy duty" or "super heavy duty". Alkaline batteries from 1700 mAh to 3000 mAh cost more than zinc-chloride batteries, but last proportionally longer.
Non-rechargeable lithium batteries are manufactured for devices that use a lot of power such as digital cameras, where their high cost is offset by longer running time between battery changes and more constant voltage during discharge.
Lithium-iron disulfide batteries can have an open-circuit voltage as high as 1.8 volts, but the in-circuit voltage reduces, making this chemistry compatible with equipment intended for zinc-based batteries. A fresh alkaline zinc battery can have an open-circuit voltage of 1.6 volts, but an iron-disulfide battery with an open-circuit voltage below 1.7 volts is entirely discharged. 
Rechargeable batteries in the AA size are available in multiple chemistries: nickel–cadmium (NiCd) with a capacity of 500–1100 mAh, nickel–metal hydride (NiMH) in various capacities of 1300–2900 mAh and lithium ion. Lithium ion chemistry has a nominal voltage of 3.6 volts. They are referred to as 14500 Li-ion batteries.
|Capacity under 50 mA constant drain||400–1700 mAh||1800–2600 mAh||2700–3400 mAh||600–1000 mAh||600–2850 mAh||1500–1800 mAh|
|Nominal voltage||1.5 V||1.5 V||1.5 V||1.2 V||1.2 V||1.65 V|
|Max. energy at nominal voltage and 50 mA drain||2.55 Wh||3.90 Wh||5.10 Wh||1.20 Wh||3.42 Wh||2.97 Wh|
In 2011, AA cells accounted for approximately 60% of alkaline battery sales in the United States. In Japan, 58% of alkaline batteries sold were AA. In Switzerland, AA batteries totaled 55% in both primary and secondary (rechargeable) battery sales.
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